(For other news from the Reuters Environment Summit, click on http://www.reuters.com/summit/GlobalEnvironment07?pid=500)

By Jeremy Lovell

LONDON, Oct 1 (Reuters) - The world went through a tipping point in dealing with climate change in 2007 as public opinion recognised the crisis, but time is running out fast for action, the head of the UN Environment Programme said on Monday.

Achim Steiner said politicians across the world, driven in part by public opinion and in part by signs of climate change like droughts and floods, were finally waking up to the need to take urgent action. What was needed now was momentum.

"We really have now got an issue on which the world public is fully engaged. Now we really have to change gear," he told Reuters by telephone from his Nairobi office. "Climate change is being observed in virtually every country."

"In 2007 we have crossed the threshold easily in terms of the kinds of issues that we agree on. We are now talking about modalities, mechanisms and money," he added.

The crunch would be at a meeting of UN environment ministers in December on the Indonesian island of Bali that many people see as a last chance to launch talks on a new world agreement on measures to cut emissions of climate changing carbon gases.

"Bali must be the starting gun. We have only 24 months to put a global framework in place," Steiner said, noting that the Kyoto Protocol on curbing greenhouse gas emissions runs to 2012 with nothing to replace it as yet.

The United States, the world's biggest emitter of carbon, has rejected Kyoto. But even there political and public pressure had forced the administration of President George W. Bush to start changing tack.

A source at a meeting of major world emitters that Bush convened in Washington last week said his officials had been taken aback by the strong pressure to act from participants.

BOTTOM LINE

"The bottom line is we are now in a much better position to have the full attention of the world's governments for the Bali meeting," Steiner said. "Kyoto is about creating a universal framework that is compatible with a global economy."

But while some countries were now taking action to cut carbon emissions, a lot more needed to be done in terms of practical actions and positive incentives to change.

"From where I sit no one is doing enough," Steiner said.

However, he noted that Germany was taking a lead in renewables like wind power and Costa Rica had adopted a low carbon economy.

Even Cuba and South Africa had started to switch to low energy lightbulbs -- although the motivating force was electricity conservation rather than global warming.

But while prospects for Bali may have begun to look slightly rosier, the impact of climate change was already being felt and would only get worse in the near term, Steiner said.

"There is no linear predictability in terms of how ecosystems respond. The phenomena of collapse is one that we have under-appreciated, partly because of the feed-back mechanisms that we are still trying to understand," he said.

Africa in particular was in the front line of global warming, yet little action and less money was being spent there to try to cope with the effects, Steiner said. "We have lost 10 years in Africa by not taking climate change seriously enough."

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